Cellular Respiration and Glycolysis
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Questions and Answers

What is the main function of the electron transport chain (ETC)?

  • To break down fatty acids for energy
  • To produce ATP directly from glucose
  • To transfer electrons and pump protons creating a proton gradient (correct)
  • To catalyse the formation of citrate from acetyl-CoA

Isocitrate dehydrogenase converts a-ketoglutarate into succinyl-CoA while producing NADH.

False (B)

What do NADH and FADH2 donate to the electron transport chain?

Electrons

The enzyme that catalyses the conversion of succinate to fumarate is called __________.

<p>succinate dehydrogenase</p> Signup and view all the answers

Match the enzymes with their corresponding reactions in the citric acid cycle:

<p>Citrate synthase = Condenses acetyl-CoA and oxaloacetate to form citrate Isocitrate dehydrogenase = Converts isocitrate to a-ketoglutarate a-ketoglutarate dehydrogenase = Converts a-ketoglutarate to succinyl-CoA Succinate dehydrogenase = Oxidizes succinate to fumarate</p> Signup and view all the answers

What is the primary product of glycolysis?

<p>Pyruvate (A)</p> Signup and view all the answers

Glycolysis occurs in the mitochondria and requires oxygen to proceed.

<p>False (B)</p> Signup and view all the answers

What is the key regulatory enzyme in glycolysis?

<p>Phosphofructokinase</p> Signup and view all the answers

The reaction catalyzed by _______ converts glucose into glucose-6-phosphate.

<p>Hexokinase</p> Signup and view all the answers

Match the following components of cellular respiration with their roles:

<p>Glycolysis = Breakdown of glucose to pyruvate Citric Acid Cycle = Oxidation of Acetyl-CoA Oxidative Phosphorylation = ATP production using electron transport Pyruvate Dehydrogenase = Conversion of pyruvate to Acetyl-CoA</p> Signup and view all the answers

Which of the following statements best describes the citric acid cycle?

<p>It produces 3 NADH and releases 2 CO2 per Acetyl-CoA. (B)</p> Signup and view all the answers

ATP is only produced in the oxidative phosphorylation stage of cellular respiration.

<p>False (B)</p> Signup and view all the answers

How many molecules of CO2 are produced for each Acetyl-CoA during the citric acid cycle?

<p>2</p> Signup and view all the answers

Flashcards

Electron Transport Chain (ETC)

The process where electrons from NADH and FADH2 are passed through a series of protein complexes embedded within the inner mitochondrial membrane, releasing energy to pump protons into the intermembrane space and ultimately drive ATP synthesis.

Citrate Synthase

The enzyme that catalyzes the condensation of acetyl-CoA and oxaloacetate to form citrate, the first step of the citric acid cycle.

Chemiosmosis

The process where ATP synthase utilizes the proton gradient created by the ETC to synthesize ATP from ADP and inorganic phosphate. This is how most ATP is generated during cellular respiration.

Oxidative Phosphorylation

The final stage of cellular respiration that occurs in the inner mitochondrial membrane, involving the electron transport chain and chemiosmosis to generate ATP.

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Pyruvate Dehydrogenase

The enzyme that converts pyruvate to acetyl-CoA, linking glycolysis to the citric acid cycle. It also releases a carbon dioxide molecule.

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What is glycolysis?

The first stage of cellular respiration that takes place in the cytoplasm, breaking down glucose (6C) into two pyruvate (3C) molecules. It's an anaerobic process (doesn't require oxygen) and can be divided into two phases: investment and payoff.

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What happens in the investment phase of glycolysis?

The investment phase requires energy (2 ATP molecules) to phosphorylate glucose and fructose-6-phosphate, preparing them for cleavage. It's like investing energy to start a process.

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What happens in the payoff phase of glycolysis?

The payoff phase generates energy (4 ATP molecules and 2 NADH molecules). The two 3C molecules are further metabolized, releasing energy. It's like getting a return on your investment.

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What does pyruvate kinase do?

An enzyme that catalyzes the conversion of phosphoenolpyruvate into pyruvate during glycolysis. This step produces ATP, a key energy molecule, which is critical for the cell's functions.

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What does the pyruvate dehydrogenase complex do?

A multi-enzyme complex that converts pyruvate into acetyl-CoA in the mitochondrial matrix. This crucial step prepares pyruvate for entry into the citric acid cycle.

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What is the citric acid cycle and what does it produce?

The citric acid cycle, also known as the Krebs cycle, completes the oxidation of acetyl-CoA. It produces 3 NADH, 1 FADH2, and 1 GTP (later converted to ATP) per acetyl-CoA. This cycle generates a significant amount of energy carrying molecules.

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What is oxidative phosphorylation?

A series of electron carriers that use the energy released from the electron transport chain to pump protons across the mitochondrial membrane, creating a proton gradient. This gradient is then used by ATP synthase to generate ATP.

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What is cellular respiration and why is it important?

Cellular respiration is a process that occurs in eukaryotic cells, breaking down glucose into ATP, a usable form of energy. This complex process involves several steps - Glycolysis, Citric Acid Cycle, and Oxidative Phosphorylation. It's vital for our survival as it powers our cells.

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Study Notes

Cellular Respiration

  • Eukaryotic cells utilize a multi-step process to convert glucose into ATP, a usable energy form.
  • This process occurs primarily in the cytoplasm and mitochondria.
  • Three main stages: Glycolysis, Citric Acid Cycle, and Oxidative Phosphorylation.
  • Enzymes are crucial for regulating and catalyzing reactions, ensuring efficiency.
  • Understanding cellular respiration is vital for advancing therapies for mitochondrial diseases.

Glycolysis

  • First stage of cellular respiration, taking place in the cytoplasm.
  • Breaks down one glucose (6C) molecule into two pyruvate (3C) molecules.
  • Anaerobic process - does not require oxygen.
  • Two phases: investment and payoff.
  • Investment phase:
    • Uses 2 ATP to phosphorylate glucose and fructose-6-phosphate.
    • Hexokinase catalyses the phosphorylation of glucose into glucose-6-phosphate trapping it in the cell.
    • Phosphofructokinase is a key regulatory enzyme, activated by AMP, inhibited by ATP.
  • Payoff phase:
    • Further metabolizes 2 3C molecules, yielding 4 ATP and 2 NADH.
    • Pyruvate kinase catalyses the conversion of phosphoenolpyruvate to pyruvate.
    • Enolase removes a water molecule, causing a double bond formation.
    • Forms 2 ATP per glucose.
  • With oxygen present, pyruvate is transported to mitochondria for further oxidation.

Citric Acid Cycle (Krebs Cycle)

  • Completes the oxidation of Acetyl-CoA.
  • For each Acetyl-CoA, produces 3 NADH, 1 FADH₂, and 1 GTP (converted to ATP).
  • Releases 2 CO₂ as waste products.
  • Key enzymes:
    • Citrate synthase: Condenses acetyl-CoA and oxaloacetate to form citrate.
    • Isocitrate dehydrogenase: Oxidizes isocitrate to α-ketoglutarate, reducing NAD+ to NADH, releasing 2 CO₂.
    • α-ketoglutarate dehydrogenase: Converts α-ketoglutarate to succinyl-CoA, reducing NAD+ to NADH, releasing CO₂.
    • Succinate dehydrogenase: Oxidises succinate to fumarate, reducing FAD to FADH₂.
  • FADH₂ carries high-energy electrons to the electron transport chain.

Oxidative Phosphorylation

  • Final stage, occurs in the inner mitochondrial membrane.
  • Two stages: electron transport chain (ETC) and chemiosmosis.
  • NADH and FADH₂ donate electrons to the ETC, a series of protein complexes and electron carriers.
  • Electrons release free energy as they move through the ETC, driving proton (H⁺) pumping into the intermembrane space.
  • ETC Complexes:
    • Complex I (NADH dehydrogenase): Oxidises NADH, transfers electrons to ubiquinone (Q), pumps protons.
    • Complex II (Succinate dehydrogenase): Transfers electrons from FADH₂ to Q, does not pump protons.
    • Complex III (Cytochrome bc₁ complex): Passes electrons from QH₂ to cytochrome c, pumps protons.
    • Complex IV (Cytochrome c oxidase): Transfers electrons to oxygen, the final electron acceptor, forming water.
  • Chemiosmosis:
    • ATP synthase uses the proton gradient to synthesize ATP from ADP and inorganic phosphate.
  • Oxidative phosphorylation produces the majority of ATP (approximately 26-28 per glucose).

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Description

Explore the intricate processes of cellular respiration, focusing on glycolysis as the first stage. Understand how eukaryotic cells convert glucose into ATP through glycolysis, the role of enzymes, and the significance of this process in cellular metabolism. This quiz will enhance your knowledge about energy production and regulation within cells.

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